Seborrhoea is a chronic skin disease that is considered to be a defect in keratinization with increased scale formulation. Dandruff is a mild form. Seborrhoea is divided into three clinical forms. Seborrhoea sicca which is characterised by dry scaling of the skin. Seborrhoea oleosa is characterised by local to diffuse scaling associated with excessive sebum. Seborrhoeic dermatitis is characterised by scaling and greasiness with gross evidence of local or diffuse inflammation. There are breed predilections for Cocker Spaniels, Springer Spaniels, Basset Hounds and, in particular, the most difficult form occurs in West Highland White Terriers. It is considered to be a primary keratinization defect of genetic origin. Although some causes are known, these if found are designated secondary seborrhoeas. Primary idiopathic seborrhoeic dermatitis is currently considered to be a chronic disease that can be ameliorated but not cured.
Standard ameliorating treatments are usually shampoos containing salicylic acid, sulphur, selenium sulphide, tars and antiseptics. These give only very temporary relief from symptoms, usually for a few days at the most.
Human seborrhoeic dermatitis has recently been associated with the yeast Malassezia (Pityrosporum) ovale. Malassezia pachydermaris has been reported to be associated with a dermatitis in dogs. However, dogs with the classic seborrhoeic dermatitis in West Highland Whites have been treated with ketaconazole tablets orally without producing a reliable cure. Symptoms re-occurred or worsened while on a treatment.